It allowed Google's cookies to be installed via adverts on
popular websites even if users' browsers' preferences had been set to
reject them. This allowed the firm to track people's web-use habits even
if they had not given it permission to do so.

Google says no personal information was collected.

'Invisible form'

Safari is the default browser on Apple's iPhones, iPads and
Macintosh computers, and is also available for PCs. When installed, its
preferences panel is set to reject tracking cookies by default.

The paper said that Google had taken advantage
of the fact that Safari allowed multiple cookies to be installed on a
device as long as its user had given permission for a first cookie to be
downloaded.

It said the search firm's code had made Safari think the user
had filled in an "invisible form" allowing the process to be triggered.

Google had previously told users that they could rely on Safari's settings to avoid it tracking them.

When the article was published the firm announced it would
halt the process. It added that the do-not-track workaround was an
unanticipated side-effect of its efforts to personalise its Google+
social network's accounts.

Negotiated penalty

A previous legal settlement with the FTC meant the agency
could fine Google a maximum of $16,000 per day for each violation of its
privacy practices.

Bearing in mind millions of users were likely to have been
affected, the sum could have been significantly larger than the
settlement fee now suggested.

The FTC declined to comment on the Journal's latest report.

A Google spokesman said the firm could not comment on the "specifics" of the case, but provided an emailed statement.

It said: "We... set the highest standards of privacy and security for our users."

"The FTC is focused on a 2009 help-centre page published more
than two years before our consent decree, and a year before Apple
changed its cookie-handling policy.

"We have now changed that page and taken steps to remove the
ad cookies, which collected no personal information, from Apple's
browsers."

Google may also face penalties from other regulators outside the US.

It is also facing probes into its Street View vehicle's collection of personal data without users' permission.